Fix: disallowUnusedParams: ignore eval exressions

Fixes #1943

Author: markelog

lib/js-file.js

@@ -823,6 +823,7 @@ JsFile.prototype = {
         if (!this._scope) {
             this._scope = escope.analyze(this._tree, {
                 ecmaVersion: 6,
+                ignoreEval: true,
                 sourceType: 'module'
             });
         }

test/specs/js-file.js

@@ -1215,6 +1215,16 @@ describe('js-file', function() {
             expect(file.getScope()).to.be.a('object');
             expect(file._scope).to.be.not.a('null');
         });
+
+        it('should ignore eval', function(done) {
+            var sources = ['function f(options) { return options; eval(); }'];
+            var file = createJsFile(sources.join('\n'));
+
+            file.iterateNodesByType(['FunctionDeclaration', 'FunctionExpression'], function(node) {
+                expect(file.getScope().acquire(node).variables[1].references.length).to.equal(1);
+                done();
+            });
+        });
     });
 
     describe('removeToken', function() {

test/specs/rules/disallow-unused-params.js

@@ -17,6 +17,11 @@ describe('rules/disallow-unused-params', function() {
         expect(checker.checkString('function a(b, c) { return c; };')).to.have.no.errors();
     });
 
+    it('should report even with eval expression (gh-1943)', function() {
+        expect(checker.checkString('function foo(options) { return options; eval() };'))
+        .to.have.no.errors();
+    });
+
     it('should not report on param that used in child scope', function() {
         expect(checker.checkString(
             'function a(b) { return function () { return b; }; }'